Intramedullary rods have been used for many years to fix fractures in the middle portion of long bones. In this technique, one or more metal rods are driven into the medullary canal of the broken bone, and through the fracture zone, leaving the rods anchored in sound bone at each end. Thus, the fracture is supported in correct position for healing. This technique has shown many benefits over alternatives such as bone plates: the patient can be mobilized and ambulated much earlier; the surgery is usually less traumatic; there is less device failure; and the bone does not suffer an excess of stress protection. Over this period, many different intramedullary rod forms have been developed, but all are basically of two types: single rods or multiple rods. Examples of single rods are those of Kuntscher, Harris (U.S. Pat. No. 4,135,507) and Halloran (U.S. Pat. No. 3,709,218). Typical multiple rod fixations are those of Ender & Ender (U.S. Pat. No. 4,169,470), Rush (U.S. Pat. No. 2,579,996), Zickel, and Herzog (U.S. Pat. No. 2,998,007).
Multiple rod use has advantages and some disadvantages over the single rod. For example, the use of a number of small diameter rods allows a precise fit in the fractured bone, but they may not impart sufficient stability for some fractures.